1. Field of the Invention
The present invention relates to a dental handpiece used in performing dental care by blowing a mixture of a powder and air on teeth along with water.
2. Description of the Related Art
There is known a dental handpiece used in blowing a mixture of a powder and air on the surfaces of teeth along with water, the powder being obtained by mixing a powder for polishing or cleaning teeth with air.
Such a dental handpiece is provided, for example, with a vessel for housing a powder, an air supply path for supplying air to the interior of the vessel, a mixture conveyance path for conveying a mixture of a powder and air to a jet nozzle, and a water conveyance path for conveying the water to be blown on the surfaces of teeth along with the mixture to a jet nozzle. In this dental handpiece, a pipe in communication with the air supply path and a pipe in communication with the mixture conveyance path are each provided in a protruding manner within the vessel, and a hole is drilled in the tip end of each of the protruding pipes so as to provide an air blowout hole and a mixture suction hole.
In a dental handpiece of this kind, it is required that a powder be mixed with air at an appropriate concentration and, therefore, there have been also proposed dental handpieces in which protruding pipes of an air blowout hole and of a mixture suction hole are arranged so that the air blowout hole and the mixture suction hole are positioned roughly in a middle region of a vessel (refer to Japanese Patent No. 3493129, for example). However, a handpiece is grasped in various positions when a dentist is performing care and, therefore, the concentration of a mixture of a powder and air in the vessel is not always appropriate. Furthermore, when a handpiece is held in such a position that the air blowout hole is buried under the powder and air supply to the interior of the vessel is stopped, the powder flows backward from the air blowout hole to the air supply path, posing problems such as the clogging of the air supply path and a decrease in the supply volume of the air.
Therefore, to solve problems as described above and thereby to provide a dental handpiece capable of obtaining an appropriate concentration of a mixture by the mixing of a powder and air within the vessel and capable of preventing the backflow of the powder to the air supply path regardless of the position of the handpiece, the applicant of the present invention has already made a proposal (refer to Japanese Patent No. 3299736, for example).
The technique based on this proposal is as follows. That is, the inside of the vessel for housing a powder therein is formed with curved surfaces so that air can swirl in all directions inside, the air supply path for supplying air to the interior of the vessel and mixing the powder and the air is divided into a plurality of branch pipes within the vessel, the branch pipes are extended to the vicinity of the curved surfaces inside the vessel in the middle region of the vessel, and a plurality of holes, which are aimed to cause the air to flow along the curved surface, are provided at the tip end of the branch pipe.
However, when a detailed examination was later made into conventional products to which the technique proposed by the applicant of the present invention was applied, it became apparent that there is room for improvement in the amount of a blown-out powder and the cutting efficiency.
That is, in conventional products, when a powder, air and water are blown, with the powder contained within the vessel to a predetermined upper limit level, it became apparent that the amount of the blown-out powder is large in the initial stage after the start of the blowout and that the amount of the blown-out powder decreases when the amount of the powder in the vessel decreases. This tendency in a change in the flow rate provides the advantage that the effect of cleaning can be easily visually ascertained in the initial stage after the start of the cleaning of the surfaces of teeth, but poses the problem that the powder filled in the vessel is used up in a short time.
Furthermore, it is requited that the cutting efficiency occurring in cleaning the surfaces of teeth by blowing a powder, air and water be constantly improved. Although the cutting efficiency may be improved simply by increasing the flow rate of the powder, the tendency that the powder in the vessel is used up in a short time is made more remarkable thereby.
The present invention has been made on the basis of such a technical problem and has as its object the provision of a dental handpiece that stabilizes the flow rate of a blown-out powder while raising the cutting efficiency and enables the stock of the powder filled in the vessel to last longer.